Lung cancer is the leading cause of cancer deaths in the United States with an estimated >160,000 deaths and >200,000 newly diagnosed cases each year. Despite the use of surgery, chemotherapy and radiation in the treatment of lung cancer, the survival rate for patients remains extremely poor (~15% over 5 years) and this survival rate has not changed appreciably over the past 20 years. Among the targeted therapies for lung cancer are small molecule inhibitors that target epidermal growth factor receptor (EGFR). Gefitinib (Iressa, Astra-Zeneca) and erlotinib (Tarceva, OSI Pharmaceuticals, Genentech) are EGFR tyrosine kinase inhibitors (TKIs) that received approval by the US Food and Drug Administration (FDA) for the treatment of patients with non-small cell lung cancer (NSCLC) after failure of prior conventional chemotherapy. However, clinical trials demonstrated that these therapeutics lack sufficient efficacy in the treatment of lung cancer, either as single agents or in combination with conventional chemotherapeutic regimes. The lack of clinical success with gefitinib or erlotinib has been explained by the existence or development of primary and secondary resistance which are governed by other molecular determinants. Asuragen was spun out of Ambion in order to focus on the medical application of RNA technologies. This proposal aims to develop novel lung cancer therapeutics based on microRNAs (miRNAs), a recently- discovered class of endogenous regulatory RNA molecules. We have identified miRNAs that induce an inhibitory response in lung cancer cells. These miRNAs are frequently deregulated in lung cancer and may govern the sensitivity to EGFR inhibitors. Therefore, we hypothesize that the combinatorial use of miRNAs and EGFR-TKIs will aid in the therapeutic response to EGFR-TKIs and diminish and/or prevent EGFR-TKI resistance. This Phase I proposal seeks to identify miRNAs that function synergistically with EGFR-TKIs in lung cancer cells with primary or secondary resistance. In combination with EGFR-TKIs, we will assess the activity of miRNAs that we have identified previously. In addition, we will perform a comprehensive miRNA microarray analysis in cells with acquired resistance using our unique DiscovArray microarrays, which profile the most comprehensive miRNA content available. We will use these profiles to identify novel miRNAs that mediate resistance and can sensitize lung cancer cells to EGFR-TKIs. PUBLIC HEALTH RELEVANCE: The research and development proposed in this application will advance human health by improving therapies for lung cancer using a newly discovered class of regulatory RNAs. The underlying technology will have broad application to other cancers and non-cancerous diseases. [unreadable] [unreadable] [unreadable]